Safety fuse



Dec. 15, 1959 E. P. ANDERSON SAFETY FUSE Filed Sept. 23, 1957 39 i6 zz.

FIG. I 28 34 26 2o 4 I I I 58 FIG. 2 60 INVENT OR.

EDWARD P ANDERSON W) 6 (J I ATTORE ZYS United States Pa SAFETY FUSE Edward P. Anderson, Livingston, NJ., assignor, by mesne assignments, to Engelhard Industries, Inc., Newark, N.J., a corporation of New Jersey Application September 23, 1957, Serial No. 685,545

7 Claims. (Cl. 20061.41)

This invention relates to a new type of safety fuse, particularly adapted for use as a protective device to prevent overspeed and bearing failure such as are sometimes encountered in aircraft turbines. The device is, however, not restricted to aircraft or other turbine applications, but can be used in many other applications where the necessity of obtaining an electrical control is applicable to a transducing switch.

Safety fuses heretofore manufactured have served to open an electrical circuit in the event of actuation of the fuse. One type of such known fuse has a ceramic stem mounted within a metal housing, with an electrical conductor being mounted on the ceramic stem. When the tip of the ceramic stem is struck by a turbine blade, for example, the ceramic stem is fractured and the electrical contact is broken, thereby opening an electrical circuit which, in the case of an aircraft turbine, stops the engine.

In accordance with the present invention, a safety fuse is provided which closes an electrical circuit upon actuation of the fuse, and referring to the accompanying drawings, two embodiments of the safety fuse of the invention are shown Fig. 1 is a view in longitudinal cross section showing one embodiment of the invention in which the fuse is mounted within a single housing, and

Fig. 2 is a view in longitudinal cross section showing the fuse having a separate two-piece housing.

Referring to Fig. 1 of the drawings, the fuse com prises a housing 2 which may be fabricated from any suitable material, such as stainless steel, and which is generally cylindrical in shape. The housing is provided with a flange 4 having the bores 6 and 8 therein, whereby the housing 2 may be secured to a turbine housing, for example. Mounted within the housing 2, is a pressure-tight vessel or container 10 having the end 12 thereof fabricated in the form of a contractible metallic-bellows. Mounted on the opposite end of the container 10 from the bellows 12, is a tip 14, which may be fabricated from a material such as tungsten carbide in order to resist abrasion forces- The end of the vessel 10 adjacent to tip 14 is hardened and necked-down at the point 16 so that when the tip 14 is struck, the vessel 10 will be ruptured at the necked-down point 16.

An insulating washer 18 is mounted on the end of the contractible metal bellows 12 and has an arm 20 supporting an electrical contact 22 mounted thereon. -A cooperating contact 24 is secured to the arm 26, the arm 26 being mounted in a fixed manner on the plug 28 having the two prongs 30 and 32 respectively secured thereto. The prong 30 is electrically connected to the arm 26 and contact 24, while the prong 32 is electrically connected by means of the wire 34 to the contact 22. A standard plug may be inserted in the end of the housing 36 to make an electrical connection with the prongs 30 and 32.

In the operation of the device of Fig. 1 of the inven- 71 2,917,594 P ten ed Dec- 1 9 I tion when mounted adjacent to theturbine in an aircraft engine, for example, the device is so mounted that there is very slight clearance between the turbine blades and the tip 14 so that should an overspeed and bearing fail ure occur, the tip 14 will be struck, resulting in a rupture of the pressure-tight vessel at the point 16. When this occurs, the pressure within the metal vessel 10 is released and the metal bellows 12 contracts, resulting in a closing of the electrical circuit between the contacts 22 and 24, which may function, if desired, to stop the flow of fuel to the engine or to perform some other operation.

Referring to Fig. 2 of the drawings, the device is shown having the housing 38 which may be fabricated from some suitable material such as stainless steel having the flange 40 thereon, the flange being provided with the bores 42 and 44 therein. A pressure-tight vessel 46 is mounted within the housing 38 and has the tip 48 thereon, the vessel 46 being provided with a necked-down portion 50 adjacent the tip 48. The pressure-tight vessel 46 is connected by means of a capillary tube 52 to a metallic bellows 54 which is mounted within a second housing 56. The housing 56 can be located at any desired point remote from the location of the housing 38. Mounted within the housing 56, are the electrical contacts 58 and 60, which operate in a manner analogous to the operation of the corresponding elements shown in Fig. 1. The operation of the device of Fig. 2 is essentially the same as that of the device of Fig. 1, since when the tip 48 is struck and the pressure-tight vessel 46 is ruptured at the point 50, an immediate decrease in pressure within the vessel occurs, and this decrease in pressure will be immediately transmitted to the bellows 54 through the capillary tube 52, resulting in a closing of the contacts 58 and 60 and the completion of an electrical circuit thereby.

The device of the invention may be easily modified to open an electrical circuit, if desired, by positioning the arm 20, in Figure 1, below the arm 26 and mounting the contact 22 on top of the arm 20 and the contact 24 on the bottom of the arm 26. Thus, when the bellows 12 contracts, the contacts will be separated, thereby opening an electrical circuit. The embodiment of the invention shown in Figure 2 may also be so modified.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is:

1. A safety fuse comprising a housing, a pressure-tight container mounted at least partially within the housing and having a contractible portion and a breakable tip thereon, first contact means mounted on the contractible portion, and fixed contact means adapted to cooperate with the first contact means.

2. A safety fuse according to claim 1 in which the contractible portion is a bellows.

3. A safety fuse according to claim 1 in which the container has a necked-down portion adjacent the tip to facilitate rupture of the container at that point.

4. A safety fuse comprising a housing, a pressure tight container mounted within the housing and having a contractible portion and a breakable tip thereon, first contact means mounted on the contractible portion, and fixed contact means adapted to cooperate with the first contact means.

5. A safety fuse according to claim 4 in which the contractible portion is a bellows.

6. A safety fuse comprising a housing, a pressure-tight first container mounted within the housing and having a breakable tip thereon, means connecting the first container to a secbnd contracfible container, first contac References Cited in the file of this patent means mounted on the co'ntr'acfible containe'r and fixed i contact means adapted to cooperate with the first con- UNITED STATES PATENTS tact means. 2,061,079 Lacoe Nov. 17, 1936 7. A safety fuse according to claim 6 in which the con- 5 2,468,509 Naab Apr. 26, 1949 tractible portion is abellows. I M 2,853,569 Neaverson Sept. 23, 1958 

